The present invention relates to a vibration damper for preventing vibration occurring on a vibration transmitting member such as various function members, frame members or the like.
For example, in a vehicle such as a motorcar, vibration of a vibration source such as an internal combustion engine or vibration caused by a road surface is transmitted to the whole vehicle body, and if a vibration transmitting member such as a function instrument attached to a body frame resonates, lowering of function or noise occurs.
Therefore, in order to suppress vibration transmitted to the vibration transmitting member, usually the vibration transmitting member is attached with a mass damper, a dynamic damper or a vibration damping device.
In the mass damper, a weight is added to the vibration transmitting member to change the natural frequency, therefore it is necessary to increase weight of the weight in order to obtain sufficient vibration reducing effect, so that weight of the vehicle body increases.
In the dynamic damper, a frequency to be suppressed is specified by spring constant of an elastic body and weight of a weight. Therefore, the dynamic damper is not effective to vibration having a plurality of resonance frequencies.
The vibration damping device comprises a plate-like vibration transmitting member and a layer or several layers of sheet-like elastic member stuck on the vibration transmitting member. In this device, the elastic member must be stuck over a somewhat large area to obtain an effect, vibration reducing function is dependent on temperature largely and sometimes the vibration damping function is lowered owing to temperature.
In a vibration damper of a former application (International Application PCT/JP98/05530), a filling at least partly made of an elastic material is inserted in an internal space of a housing fixed to a vibration transmitting member with a gap not bonded to the housing. According to this vibration damper, since vibration is reduced owing to energy loss caused by sliding friction and impact when the filling touches an inner surface of the housing, plural resonance vibrations of different frequencies can be suppressed effectively. Further, the vibration damping owing to energy loss by sliding friction and impact is little influenced by temperature. The vibration damping effect becomes larger as the impact speed increases, therefore the damping effect is obtainable especially at a resonance region of high frequency. Accordingly, regarding a low resonance frequency, the vibration damping effect can not be expected so much. Also the vibration damper is not effective when it is intended that plural resonance vibrations are damped and a specific frequency is damped particularly largely.
Japanese Laid-Open Patent Publication Hei 8-127347 discloses an example for suppressing vibration of a steering wheel by a dynamic damper. However, management of resonance frequency deviation on mass-production is not easy.
The present invention has been accomplished in view of the foregoing and an object of the invention is to provide a vibration damper little depending on temperature capable of damping plural resonance vibrations over a wide frequency region as well as damping a specific frequency vibration. Another object of the invention is to provide a vibration damper capable of reducing deviation of resonance frequencies on mass-production and suppressing vibration of a steering wheel effectively.
In order to achieve the above objects, the present invention provides a vibration damper, comprising: a housing formed of a rigid material, having an internal space and fixed to a vibration transmitting member; an elastic body inserted in the internal space not bonded to the housing with a gap in a direction of vibration of the housing; and a weight integrally supported by the elastic body so as not to touch the housing, thereby the elastic body and the weight form a dynamic damper.
Owing to the construction that the elastic body is inserted in the inner space of the housing, vibration is damped based on energy loss caused by sliding friction and impact occurring when the elastic body touches the inner surface of the housing. Therefore, vibration damping effect is obtainable regarding plural resonance vibrations of different frequencies and dependence on temperature is small.
A resonance vibration in a specific frequency region which can not be damped by the above construction or a resonance vibration wanted to be cancelled especially can be damped by the construction that the weight is supported by the elastic body to form a dynamic damper. Thus, vibration damping effect can be obtained regarding plural resonance vibrations in a wide frequency range.
The weight may be provided within the elastic body. The weight can be supported by the elastic body integrally not touching the housing by the simple construction and the vibration damper can be made small and light.
Spring constant of the elastic body and weight of the weight may be set so that the dynamic damper cancels a specific frequency vibration. Owing to the construction that the elastic body is inserted within the housing fixed to the vibration transmitting member not bonded to the housing with a gap in a direction of vibration of the housing, vibration damping effect is obtainable regarding plural resonance vibrations of different frequencies, and also vibration in a frequency region which can not be damped by the construction or vibration of a specific frequency to be damped especially can be damped by the dynamic damper.
The above-mentioned specific frequency vibration may be a low frequency vibration. According to the construction that the elastic body is inserted within the housing fixed to the vibration transmitting member not bonded to the housing with a gap in a direction of vibration of the housing, vibration is damped based on energy loss caused by sliding friction and impact, therefore the vibration damping effect is larger especially in a high frequency resonance region.
Therefore, regarding a low frequency resonance region, vibration damping property is obtained by suitably setting spring constant of the elastic body and weight of the weight in the dynamic damper. Thus, vibration damping effect can be obtained regarding plural resonance vibrations in substantially overall frequency region.
According to another aspect of the invention, there is provided a vibration damper, comprising a housing formed in a cylinder from a rigid material, having an internal space, and fixed to a steering wheel with axis of the cylinder directed substantially in parallel with a steering shaft; an elastic body inserted in the internal space not bonded to the housing with a gap in a direction of vibration of the housing; and a weight integrally supported by the elastic body so as not to touch the housing.
Owing to the construction that the housing is fixed to the steering wheel with axis of the cylinder directed substantially in parallel with the steering shaft and the elastic body is inserted in the internal space not bonded to the housing with a gap in a direction of vibration of the housing, the elastic body touches an inner surface of the housing corresponding to vibration in the direction perpendicular to the steering shaft of the steering wheel to suppress the vibration based on energy loss caused by sliding friction and impact. Therefore, vibration damping effect is obtained regarding plural resonance vibrations of different frequencies. An exact setting of the resonance frequency, which is necessary in a dynamic damper, is not necessary so that deviation of the resonance frequency on mass-production can be reduced. Since vibration damping effect is obtained effectively by the weight of relatively small mass, the vibration damper can be applied to a steering wheel easily.
In the last-mentioned vibration damper, a plurality of the weights may be provided. Even if the total mass of the weights is the same as a mass of a weight in a case having single weight, vibration is damped more and degree of freedom for layout of the weight is improved.
In the above-mentioned vibration damper, a plurality of the elastic bodies each supporting the weight may be provided. Each elastic body integrally supporting the weight is small, so that degree of freedom of layout and shape of the housing is high.
The elastic body and the weight may form a dynamic damper. While plural resonance vibrations of different frequencies can be damped generally, the dynamic damper is capable of damping a specific frequency necessitating to be damped especially, therefore vibrations in a wide frequency region can be damped more effectively.